Additive for corrosion control

ABSTRACT

An additive comprising tris (2-carboxyethyl) phosphine (“TCEP”) and/or tris (3-hyroxypropyl) phosphine (“THPP”) may be added to an aqueous system in an effective amount to inhibit corrosion of the metallurgy within the aqueous system, wherein the additive may be in the form of a solution and maintains its stability and effectiveness in inhibiting corrosion in a wide range of temperature, pressure, and pH conditions of the aqueous system.

TECHNICAL FIELD

The present invention relates to methods and additives to inhibit corrosion of metallurgy that may be found in an aqueous system, and in particular, the introduction of a corrosion inhibition additive comprising tris (2-carboxyethyl) phosphine (“TCEP”) and/or tris (3-hyroxypropyl) phosphine (“THPP”) to inhibit corrosion in an aqueous system.

BACKGROUND

There has always been a concern to better protect metal surfaces that exist within an aqueous system against corrosion in general, such as rusting, as well as pitting corrosion, a specific type of corrosion concentrated in a certain area that forms a pit or divot in the surface of the metal. This is particularly true for aqueous systems to which an acid is intentionally added for a particular purpose. Corrosion, if unattended, may result in failure or destruction of the metal, causing the particular water system to be shut down until the necessary repairs can be made, driving up the maintenance costs. In addition, the inconvenient and varying chemical conditions of many of the aqueous systems and the stability of the disulfide compounds in water that lead to corrosion make corrosion and rust control of metal pipes and equipment and other metallurgy employed in those systems even more difficult.

To date, a variety of corrosion inhibition additives have been developed to help inhibit corrosion in aqueous systems in a cost-efficient manner, especially systems in which the metal surfaces are exposed to brine.

In some instances, corrosion control additives comprising thiols, such as β-mercaptoethanol (“BME”) and Dithiothreitol (“DTT”), have been employed to reduce corrosion and remove rust. Both compounds have been found to be useful in the reduction and management of corrosion in aqueous systems. However, BME, in particular, can be volatile and has a tendency to evaporate from the solution medium in which it used, which means the concentration of BME in the solution decreases with time. As a result, BME must be applied in large amounts to achieve the desired results. And, while DTT is less volatile than BME, the DTT molecule is often altered from a straight chain structure to a ring structure during the disulfide reduction reaction that takes place when the thiol is being applied to aqueous environments for corrosion control and becomes less stable in basic (high pH) conditions.

Thus, it is desirable to employ more stable, cost-effective corrosion inhibitor compounds to reduce corrosion of metallurgy in aqueous systems in a wider range of chemical conditions.

SUMMARY

There is provided, in one form, a method for inhibiting corrosion of metallurgy in an aqueous system, the method comprising introducing in an effective amount of an additive comprising TCEP and/or THPP to an aqueous system in contact with metallurgy for inhibiting corrosion of the metallurgy in the aqueous system. In one non-limiting embodiment, the additive is introduced to the aqueous in an amount ranging from about 5 parts per million (“ppm”) to about 50,000 ppm based on the total volume of the fluid in the system. In another non-restrictive version, the pH of the aqueous system ranges from about 1.5 to about 9.

There is also provided a treated aqueous system, wherein the treated aqueous system comprises an aqueous system in contact with metallurgy and an effective amount of additive comprising TCEP and/or THPP, the amount of the additive being effective to inhibit corrosion of the metallurgy contacting the aqueous system, wherein the additive may be in the form of solution.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are two photographic illustrations showing the equipment and setup of the kettle testing system used to determine corrosion rate of the corrosion inhibition additives evaluated;

FIG. 2 is a graphic illustration comparing the corrosion rate of various concentrations of a 2-mercaptoethanol based additive and a TCEP-based additive in synthetic brine;

FIG. 3 is a graphic illustration comparing the corrosion rate of various concentrations of a 2-mercaptoethanol-based additive and a THPP-based additive in synthetic brine; and

FIGS. 4A and 4B are a photographic and graphic illustration showing the performance of a corrosion inhibition additive comprising heat and pressure treated TCEP as compared to the performance of a corrosion inhibition additive comprising heat and pressure treated 2-mercaptoethanol.

DETAILED DESCRIPTION

It has been discovered that an additive comprising TCEP and/or THPP may be added to an aqueous system having metallurgy to effectively inhibit corrosion of the metallurgy in the system in a wide range of system conditions. It has been discovered that additives comprising TCEP and/or THPP exhibit stability in low and high pH conditions and when subjected to heat treatment and may reduce or control corrosion under such conditions.

“Aqueous system” is defined herein to include an aqueous fluid (a fluid containing water) and any components or any metallurgy (e.g. pipes, tanks, conduits, or vessels) through which the aqueous fluid may flow or along or outside of which the aqueous fluid may flow. The aqueous fluid may be or include, but is not limited to, water, brine, seawater, a hydrocarbon fluid containing water, and combinations thereof. In one embodiment, the hydrocarbon stream containing water is free of hydrogen sulfide.

In a non-limiting embodiment, the aqueous fluid may circulate through an oil and gas production system, an oil and gas refining system, a cooling tower, a cooling water system, an air-conditioning system, a boiler, a wastewater treatment system, a deionized water system, and combinations thereof. The cooling tower may be or include an open loop cooling tower, a closed loop cooling tower, and combinations thereof. ‘Open loop’ differs from ‘closed loop’ in that the ‘open loop’ system has recirculating water therethrough.

As used herein, metallurgy is any metal or metal alloy surface that may be corroded. The types of metal surface that may be corroded include, but are not limited to, an iron-containing surface, such as steel; an aluminum-containing surface; yellow metal surfaces, such as copper and copper alloys, and combinations thereof.

The additive may be comprised of TCEP or THPP or combinations of the two. The amount of TCEP and/or THPP in the additive may range from 10 wt. % to 15 wt. %, based on the total weight of the additive.

In one non-limiting embodiment, the additive is in the form of a solution, in which the solvent may be selected from a group consisting of water, methanol, propanol, ethylene glycol, and combinations thereof. The amount of TCEP and/or THPP in the solution ranges from about 10% to about 15% based on a total volume of fluid in the additive solution. In one non-limiting embodiment, the additive is prepared from a sample of solid TCEP-HCl to make a 15 vol. % TCEP stock solution. In some cases, a 0.5 M TCEP solution, which is about 14.5 vol. % TCEP, may be used.

The amount of the additive to be applied to the aqueous system for corrosion control may range from about 5 parts per million (“ppm”) independently to about 50,000 ppm based on the total volume of fluid in the aqueous system, alternatively from about 10 ppm independently to about 10,000 ppm, based on the total volume of fluid in the aqueous system, or from about 25 ppm independently to about 400 ppm, based on the total amount of fluid in the aqueous system. In one example, the amount of the corrosion inhibition additive comprising TCEP applied to a synthetic brine may range from about 5 ppm to about 600 ppm. As used herein with respect to a range, “independently” means that any threshold may be used together with another threshold to give a suitable alternative range, e.g. an amount from about 10 ppm to about 400 ppm is also considered a suitable alternative range.

In another non-limiting embodiment, the aqueous system may optionally contain other compounds such as, but not limited to, a scale dissolver, a biocide, a chlorine-containing component, a surfactant, a dispersant, a passivator, and combinations thereof.

A scale dissolver may be used if scales other than iron-based scales are present in the aqueous system. Such scale dissolvers include, but are not limited to, hydrochloric acid, sulfuric acid, and combinations thereof.

Examples of dispersants useful for dispersing solid debris in the aqueous system include, but are not necessarily limited to, polyacrylates, polymaleates, polycarboxylic acids, their homopolymers, copolymers, terpolymers and combinations thereof.

Suitable passivators, such as nitrites, polyhydroxycarboxylic acids, polyhydroxycarboxylic acids salts, and combinations thereof, may be included in the system during and after cleaning of the metallurgy.

Useful surfactants may be nonionic, cationic, anionic, zwitterionic and combinations thereof.

The biocide may be or include, but is not limited to, sodium hypochlorite (also known as bleach), NaHClO, chlorine dioxide, chlorine, bromine, non-oxidizing biocides, and combinations thereof. Non-limiting examples of the non-oxidizing biocides may be or include isothiazoline; glutaraldehyde; 2,2-dibromo-3-nitrilopropionamide (DBNPA); and combinations thereof.

The aqueous system is stable in the presence of chlorine-containing components, such as chloride salts. The chlorine-containing components may be optionally present in the aqueous system prior to the addition of the glucaric acid and/or glucaric acid salt additive. Alternatively, the chlorine-containing components may be added to the aqueous system at the same time or different time as the additive disclosed here and be in an amount ranging from about 1 ppm independently to about 1,000 ppm, alternatively from about 50 ppm independently to about 800 ppm, or an amount greater than about 250 ppm in another non-limiting embodiment.

The additive may be used to inhibit corrosion of metallurgy in an aqueous system having a wide variety of pH values. The pH of the system may be less than about 7, alternatively from about 3 independently to about 5, where it has been shown that an additive containing TCEP retains its sulfide reducing power, or from about 1 independently to about 3 in another non-limiting embodiment. The aqueous system may also have a low pH, such as, without limitation, from about 1.5 independently to about 3, or a high pH, such as, for example, a pH higher than 7.5 or from about 7 independently to about 9. In one embodiment, it is shown that TCEP is odorless and soluble in water up to 310 mg/ml at a pH of 2.5.

When used herein, the term “inhibition” means the additive may suppress, reduce, or prevent further rust formation and/or corrosion of the metallurgy within the aqueous system. That is, it is not necessary for rust or corrosion to be entirely prevented or removed for the methods or systems discussed herein to be considered effective, although complete removal or prevention is a desirable goal. Success is obtained if less rust formation or corrosion occurs using the additive than in the absence of the additive. Alternatively, the methods and systems described are considered successful if there is at least a 50% decrease in rust formation and/or other corrosion within the aqueous system.

The invention will be further described with respect to the following Examples, which are not meant to limit the invention, but rather to further illustrate the various embodiments.

EXAMPLES

The effect of an additive containing TCEP on brine corrosivity was evaluated using kettle testing. The corrosion rate upon carbon steel coupons with different surface finishes were evaluated in the absence or presence additives comprising TCEP, THPP, or 2-mercaptoethanol (U1125) in varying amounts in a synthetic brine. Corrosion rates were evaluated using the kettle test set up shown in FIG. 1A. As shown in FIG. 1B, the three-electrode electrochemical system was used to measure the corrosion rate by the linear polarization resistance (LPR) method. Two surface finishing methods were used to prepare the working electrode: 1) media blasting with 80-grit aluminum oxide (−106 to 212-μm nominal diameter), 2) manual polishing with 320- and 600-grit sandpaper sequentially to a mirror finish. Testing was conducted at 25° C. and at atmospheric pressure for 18 hours.

FIG. 2 is a graphic illustration comparing the corrosion rate of various concentrations of a 2-mercaptoethanol based additive and a TCEP-based additive in synthetic brine. The data in FIG. 2 indicate that TCEP-based additive showed concentration dependent inhibition of corrosion compared to negative control where no corrosion inhibitor is used and that the 2-mercaptoethanol-based additive applied to the synthetic brine as positive control for corrosion inhibition showed complete inhibition of corrosion.

Similarly, the data in FIG. 3 indicates that a THPP-based corrosion inhibition additive showed 63% less corrosion at 100 ppm compared to negative control where no corrosion inhibitor is used and that the 2-mercaptoethanol-based additive (U 1125) showed complete inhibition of corrosion.

In another evaluation, additive samples of a 0.5M TCEP solution and 90-95% 2-mercaptoethanol were taken and placed in a high temperature/pressure bomb of 300 psi pressure in a container and sealed. The container containing the additive samples was incubated at 300° F. for one week. The container was removed and cooled to room temperature for few hours and samples were collected and used for corrosion inhibition functional testing.

As shown in the photographic illustration in FIG. 4A, formation of white solid in the 90-95% 2-mercaptoethanol sample occurred while TCEP-based sample remained as a clear liquid. In addition, the results of the corrosion inhibition functional testing of both samples indicated similar corrosion inhibition after heat treatment as exhibited in FIGS. 2 and 3. See graphic illustration in FIG. 4B.

In the foregoing specification, the invention has been described with reference to specific embodiments thereof. However, it will be evident that various modifications and changes can be made thereto without departing from the broader spirit or scope of the invention as set forth in the appended claims. Accordingly, the specification is to be regarded in an illustrative rather than a restrictive sense. For example, aqueous systems, metallurgy, equipment, specific aqueous fluids, phosphines, additives, components, scale dissolvers, surfactants, corrosion inhibitors, dispersants, passivators, biocides, and chlorine-containing components falling within the claimed parameters, but not specifically identified or described in a particular embodiment, are expected to be within the scope of this invention.

The present invention may suitably comprise, consist or consist essentially of the elements disclosed and may be practiced in the absence of an element not disclosed.

For example, the methods for inhibiting corrosion of metallurgy in contact with an aqueous system may consist of or consist essentially of adding TCEP and/or THPP in an effective amount to inhibit corrosion of the metallurgy in an aqueous system. Alternatively, the additive may consist essentially of or consist of TCEP and/or THPP alone or together with any optional components that do not materially affect the basic and novel characteristics of the invention claimed.

In another non-restrictive version, a treated aqueous system may consist essentially of or consist of an aqueous system in contact with metallurgy and TCEP and/or THPP, wherein the amount of the additive present is effective to inhibit corrosion within the aqueous system. Alternatively, additive may consist essentially of or consist of TCEP and/or THPP or together with any optional components that do not materially affect the basic and novel characteristics of the invention claimed.

As used herein, the terms “comprising,” “including,” “containing,” “characterized by,” and grammatical equivalents thereof are inclusive or open-ended terms that do not exclude additional, unrecited elements or method acts, but also include the more restrictive terms “consisting of” and “consisting essentially of” and grammatical equivalents thereof. As used herein, the term “may” with respect to a material, structure, feature or method act indicates that such is contemplated for use in implementation of an embodiment of the disclosure and such term is used in preference to the more restrictive term “is” so as to avoid any implication that other, compatible materials, structures, features and methods usable in combination therewith should or must be, excluded.

As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise.

As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.

As used herein, the term “about” in reference to a given parameter is inclusive of the stated value and has the meaning dictated by the context (e.g., it includes the degree of error associated with measurement of the given parameter). 

What is claimed is:
 1. A method for inhibiting corrosion upon metallurgy in contact with an aqueous system comprising: introducing an additive comprising tris (2-carboxyethyl) phosphine (“TCEP”) and/or tris (3-hyroxypropyl) phosphine (“THPP”) to the aqueous system in contact with the metallurgy, the amount of the additive being effective to inhibit corrosion of the metallurgy within the aqueous system.
 2. The method of claim 1, wherein the amount of TCEP and/or THPP present in the additive ranges from about 10 wt. % to about 15 wt. %.
 3. The method of claim 1, wherein the additive is in the form a solution.
 4. The method of claim 3, wherein solution contains a solvent selected from a group consisting of water, methanol, propanol, ethylene glycol, and combinations thereof.
 5. The method of claim 1, wherein the effective amount of the additive ranges from about 5 ppm to about 50,000 ppm based on a total volume of fluid in the aqueous system.
 6. The method of claim 1, wherein the aqueous system is selected from the group consisting of an aqueous fluid, a hydrocarbon fluid containing water, a cooling tower, a cooling water system, a wastewater treatment system, and combinations thereof.
 7. The method of claim 1, wherein the aqueous system further comprises at least one additional component selected from the group consisting of a scale dissolver, a biocide, a chlorine-containing component, a surfactant, a dispersant, a passivator, and combinations thereof.
 8. The method of claim 1, wherein the aqueous system has a pH from about 1.5 to about
 9. 9. A treated aqueous system comprising: an aqueous system in contact with metallurgy; and an effective amount of additive comprising TCEP and/or THPP, the amount of the additive being effective to inhibit corrosion of the metallurgy contacting the aqueous system.
 10. The treated aqueous system of claim 9, wherein the effective amount of the additive ranges from about 5 ppm to about 10,000 ppm based on the total volume of fluid in the aqueous system.
 11. The treated aqueous system of claim 10, wherein the effective amount of the additive ranges from about 10 ppm to about 600 ppm based on the total volume of fluid in the aqueous system.
 12. The treated aqueous system of claim 9, wherein the additive is in the form of a solution.
 13. The treated aqueous system of claim 12, wherein the amount of TCEP and/or THPP in the solution ranges from about 10% to about 15% based on a total volume of fluid in the additive solution.
 14. The treated aqueous system of claim 9, wherein the aqueous system is selected from the group consisting of an aqueous fluid, a hydrocarbon fluid containing water, a cooling tower, a cooling water system, a wastewater treatment system, and combinations thereof.
 15. The treated aqueous system of claim 9, wherein the aqueous system further comprises at least one additional component selected from the group consisting of a scale dissolver, a biocide, a chlorine-containing component, a surfactant, a dispersant, a passivator, and combinations thereof.
 16. The treated aqueous system of claim 15, wherein the surfactant is selected from the group consisting of a nonionic surfactant, a cationic surfactant, an anionic surfactant, a zwitterionic surfactant, and combinations thereof.
 17. The treated aqueous system of claim 15, wherein the passivator is selected from a group consisting of nitrite, polyhydroxycarboxylic acid, polyhydroxycarboxylic acid salt, and combinations thereof.
 18. The treated aqueous system of claim 15, wherein the biocide is selected from a group consisting of sodium hypochlorite, NaHClO, chlorine dioxide, chlorine, bromine, a non-oxidizing biocide, and combinations thereof.
 19. The treated aqueous system of claim 15, wherein the scale dissolver is selected from a group consisting of hydrochloric acid, sulfuric acid, and combinations thereof.
 20. The treated aqueous system of claim 9, wherein the aqueous system has a pH greater than about 7.5. 